Effects of Sr Doping on the Thermoelectric Properties of Ca_3Co_4O_9-based Materials

Polycrystalline Ca3-xSrxCo4O9(x=0-0.5) ceramics were prepared by the sol-gel method combined with the ordinary pressing sintering and the thermoelectric properties were measured from room temperature to 673 K.The Sr doping had a greater impact on the thermoelectric properties of Ca3Co4O9.The conductivity increased significantly as the Sr content increasing,and the Seebeck coefficient decreased slightly.Sr doping could reduce the thermal conductivity observably,and with the doping content increasing,the decrease amplitude of the thermal conductivity increased gradually.These results indicated that the thermoelectric properties of the material could be optimized remarkably with the Sr doping.The themoelectirc figure of merit Z reached 1.07×10-4 K-1 at 573 K for the sample of Ca2.5 Sr0.5Co4O9.